Sorbent and devices for capturing, stabilizing and recovering volatile and semi-volatile compounds

ABSTRACT

The present invention provides an improved sorbent and corresponding device(s) and uses thereof for the capture and stabilization of volatile organic compounds (VOC) or semi-volatile organic compounds (SVOC) from a gaseous atmosphere. The sorbent is capable of rapid and high uptake of one or more compounds and provides quantitative release (recovery) of the compound(s) when exposed to elevated temperature and/or organic solvent. Uses of particular improved grades of mesoporous silica are disclosed.

FIELD OF THE INVENTION

The present invention concerns systems, apparatuses, and methods used tocapture, stabilize, and recover volatile and semi-volatile compounds.More particularly, the invention concerns sorbent materials useful insampling chemical vapors for area monitoring and personal exposuremonitoring through the application of diffusive samplers (passivedosimeters). The invention also includes a means of pre-concentratingchemical vapors present in very small amounts to facilitate atmosphericsampling.

BACKGROUND OF THE INVENTION

Industrial, medical, office, and military personnel, as well as peoplewho live or work in residential buildings, can be exposed to a broadrange of potentially toxic compounds. This potential for exposure makesenvironmental monitoring important. However, in some cases monitoringproves difficult, because the person may be highly mobile throughout theday or week; and move from one potential exposure area to the next. Inother cases, the person may be working or living in a rugged andsometimes remote location that requires sending collected samples to adistant lab for analysis. Also, there is always a possibility that aperson may be exposed to an unknown or unidentified toxic compound whoseeffect may not be known or experienced until long after the exposureends.

The art discloses devices for capture of volatile compounds: U.S. Pat.Nos. 9,370,749, 7,955,574, 9,412,573, 9,914,087, 9,901,843, 9,783,417,9,643,186, 9,249,241, 9,079,049, 8,955,515, 8,668,873, 8,561,484,8,500,852, 8,011,224 and 7,295,308, 9,370,749 to Addleman et al.discloses a porous multi-component material for capture and separationof species of interest. The material includes a substrate and acomposite thin film, which comprises a combination of porous polymer andnanostructured material. The requirement of the porous polymer alongwith the nanostructured material is disadvantageous, because there is asignificant potential of thermal degradation of the porous polymerduring thermal desorption analysis of the composite thin film and asignificant potential of contamination, by monomeric and dimericspecies, of an extract during solvent extraction of the composite thinfilm.

Apblett et al. (“Synthesis of mesoporous silica grafted with3-glycidylpropyltrimethoxy-silane” in Mater. Let. (2009), 63(27),2331-2334; “Preparation of mesoporous silica with grafted chelatingagents for uptake of metal ions” in Chemical Engineering Journal (2009),155(3), 916-924; “Metal ion adsorption using polyamine-functionalizedmesoporous materials prepared from bromopropyl-functionalized mesoporoussilica” in Journal of Hazardous Materials (2010), 182, 581-590;“3-Aminopropyltrimethoxysilane functionalized mesoporous materials anduptake of metal Ions” in Asian J. Chem. (2011), 23(2), 541-546) disclosethe synthesis of mesoporous silica covalently grafted with variousdifferent silane groups, e.g. 3-glycidylpropyl-silane,3-aminopropyl-silane, by treatment of mesoporous silica (OSU-6-W) with atrialkoxysilane or trihalosilane. The material was used for adsorptionof divalent transition metal from aqueous solution. The OSU-6-W wasprepared according to a modified method of Tuel et al. (“Synthesis andCharacterization of trivalent metal containing mesoporous silicasobtained by a neutral templating route” in Chem. Mater. (1996), 8, 114)or according to a modified method of Apblett et al. (“Preparation ofmesoporous silica with grafted chelating agents for uptake of metalions” in Chemical Engineering Journal (2009), 155(3), 916-924).

Mesoporous silica of the MCM-41 type (hexagonal; CAS 7631-86-9; linearformula SiO₂; MW 60.08) is available from Sigma Aldrich (Milwaukee,Wis.) and is known to possess the following physical properties.

Linear formula SiO₂ Form White powder Pore size (diameter) 2-10 nm Porevolume 0.5-2.0 cm³/g Surface area ~1000 m²/g (BET)

Additional grades of MCM-41 mesoporous silica are also available.

Prior art monitoring devices, such as area sensors and personaldosimeters, also make use of passive sampling media such as activatedcharcoal and complex polymers. While this media can capture a variety ofvolatile and semi-volatile compounds, its capacity, rate of uptake, andstorage stability are limited. For example, storage stability istypically limited to about 14 to 28 days post-exposure. This length oftime can be too short where collected samples must be sent to a distantlab or where the sample must be stored for longer periods of time forfuture analysis or identification.

It would be a significant advance in the field of monitoring of volatileorganic compounds and semi-volatile organic compounds to provide adevice with the ability to capture extremely low to high amounts of awide array of structurally diverse target compound(s) while at the sametime being capable of long-term storage without excessive desorption ordegradation of the captured compound(s). It would also be a significantadvance in the field to provide devices comprising sorbent excludingorganic polymers, which can interfere with thermal desorption-based andextraction-based methods for quantitation of the captured compounds.

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved sorbent andcorresponding devices that overcomes one or more disadvantages of knownmonitoring devices. The sorbent and device of the invention are capableof capturing and stabilizing low to high amounts of one or more volatileorganic compound(s) (VOC) or semi-volatile organic compound(s) (SVOC)present in a gaseous environment, i.e. airborne VOC or SVOC. The sorbentalso facilitates subsequent quantitative recovery of the capturedcompound(s). The device can be a dosimeter, a training device, apreconcentrator, a filter, or other know device for capturing and/ortemporarily retaining VOC or SVOC.

The sorbent can also be incorporated into a training device and trainingmethods. In one aspect, the training device comprises a substrate(body), and sorbent medium onto which one or more VOC or SVOC has beenadsorbed. The training device can be used to train animals that senseairborne VOC or SVOC compounds or as controls for other devices(instruments) that sense airborne VOC or SVOC compounds.

The dosimeter can be used to monitor the presence of such compounds in agaseous environment, such as a work area. Embodiments of the dosimeterwith adsorbed VOC or SVOC exhibit long-term storage stability for up to18 weeks with regard to the adsorbed compound(s), meaning the adsorbedcompound undergoes little to no degradation or desorption during storageat room temperature or in a refrigerator (+6° C. to +24° C.). Of anexceptional advance is the sorbent ability to stabilize reactive specieswithin the nanopores at room temperature. Such species would chemicallyreact with typical polymer-based dosimeters even under refrigeration.

The device of the invention can be adapted to almost any known format ofpassive sampling device. It can be a badge, rod, tube, pen, plate, orany other form that allows contact with the environment.

One aspect of the invention provides a device comprising a sorbent (aporous medium) that, at ambient conditions, passively captures (adsorbs,entraps) one or more VOC or SVOC present in a gaseous atmosphere, i.e.one or more airborne VOC or SVOC, and, when exposed to elevatedtemperatures or organic solvent, releases the captured one or morecompounds. This means the VOC or SVOC can be removed from the sorbent bythermal desorption and/or solvent extraction. The porous medium isadhered onto a substrate and does not require inclusion of a porouspolymer or other polymer within the porous medium to adhere the porousmedium onto the substrate. The sorbent may be in powder, pellet form, orapplied on the surface of a substrate.

The sorbent can be applied onto the substrate uniformly ornon-uniformly. The layer(s) of sorbent on the substrate can be dividedinto two or more sections. Each section may comprise the same amount ofsorbent, or two or more of the sections may comprise different amountsof sorbent. The substrate can also be sectioned. (FIGS. 6A and 6B) Thesections can be separated and stored for different purposes, e.g.immediate sampling, sample archiving (storage), etc.

Specific embodiments of the invention include those wherein: a) theporous medium is nanoporous; b) the porous medium comprises silica; c)the porous medium comprises nanoporous silica; d) the porous mediumfurther comprises one or more adsorption modifiers; e) the dosimetercomprises a body (substrate) onto which the porous medium has beenapplied; f) the porous medium excludes a porous polymer; g) the porousmedium is non-covalently bound to the substrate; h) the porous mediumcomprises mesoporous silica; g) the porous medium comprises mesoporoussilica of the MCM-41 type having hexagonal cylindrical (tubular) porestructure; and/or h) the sorbent (porous medium) excludes an organicpolymer. The mesoporous silica can also be dispersed in a supportmaterial such as glass wool to fabricate filters.

In some embodiments, the sorbent (porous medium) is a functionalizedsorbent, meaning it has been functionalized with one or more adsorptionmodifier functional groups that improve (in at least one aspect) theadsorption of particular VOC or SVOC. Embodiments of the inventioninclude those wherein: a) the one or more adsorption modifier functionalgroups are covalently bound to the porous medium; b) the one or moreadsorption modifier functional groups are non-covalently bound to theporous medium; c) the mass content of functional groups in the porousmedium as determined by thermogravimetric analysis is in the range of20-25%; or d) a combination of any two or more thereof.

The sorbent can comprise a single porous medium or a combination ofporous mediums. Embodiments of the invention include those wherein: a)the sorbent comprises non-functionalized mesoporous silica; b) thesorbent comprises functionalized mesoporous silica; c) the sorbentcomprises a mixture of non-functionalized mesoporous silica and one ormore functionalized mesoporous silicas; or d) the sorbent comprises amixture of non-functionalized mesoporous silica, a first functionalizedmesoporous silica, and a second functionalized mesoporous silica. Theweight ratio of non-functionalized mesoporous silica to functionalizedmesoporous silica can range from about 1:100 to about 100:1.

Grafting of mesoporous silica with biphenyl- andmethoxytriethylenoxypropyl-functional groups in many cases increases itsaffinity to non-polar and polar VOC, respectively. In various mixes offunctionalized and non-functionalized sorbents, the contents offunctionalized sorbent ranges between 0 to about 30 wt % with theremainder comprising the non-functionalized sorbent. In someembodiments, the composition comprises: a) about 50 wt % ofnon-functionalized sorbent, about 30 wt % of biphenyl-functionalizedsorbent, and about 20 wt % of methoxytriethylenoxypropyl-functionalizedsorbent; b) about 40-60 wt % of non-functionalized sorbent, about 40-20wt % of biphenyl-functionalized sorbent, and about 30-10 wt % ofmethoxytriethylenoxypropyl-functionalized sorbent; or c) about 30-70 wt% of non-functionalized sorbent, about 1-50 wt % ofbiphenyl-functionalized sorbent, and about 1-40 wt % ofmethoxytriethylenoxypropyl-functionalized sorbent.

In some embodiments, the functionalized sorbent of the inventionexhibits increased uptake rate, slower rate of desorption, and decreasedmaximum uptake capacity as compared to the native non-functionalizedsorbent.

The porous medium releases the adsorbed (captured or entrapped) volatileorganic compound(s) (VOC) or semi-volatile organic compound(s) (SVOC)when the porous medium is exposed to heat or reduced pressure or organicsolvent. The porous medium releases at least about 75%, at least about80%, at least about 85%, at least about 90%, at least about 92.5%, atleast about 95%, at least about 97.5%, at least about 99%, or all of theadsorbed VOC or SVOC when subjected to tests for quantitation of theadsorbed compound(s). In other words, the porous medium provides atleast 75% recovery of VOC or SVOC. In some embodiments, the porousmedium quantitatively releases the adsorbed compound(s). The porousmedium stabilizes and protects adsorbed VOC and SVOC from decompositionfor a period of at least about 30 days or more.

The sorbent (porous medium) exhibits different affinities (adsorptioncapacity) for different classes VOC's or SVOC's differing in vaporpressure. The sorbent can be used to adsorb compounds having a vaporpressure ranging from very low (such as 0.013 kPa for naphthalene) tovery high (such as 101 kPa for acetaldehyde). Accordingly, the sorbent(and corresponding device(s)) is suitable for adsorption of compoundshaving a vapor pressure≥0.00002 mmHg.

Embodiments of the invention include those wherein the porous medium canadsorb compounds from one or more of the following classes of compounds:aromatic hydrocarbon, non-aromatic hydrocarbon, alkylhalide,alkylaldehyde, polar organic compound, non-polar organic compound,explosive, narcotic, controlled substance, illegal substance, industrialchemical, commodity chemical, pesticide, herbicide, poison, solvent,nitramines, pyrethroids, nitroaromatics, tetrazoles, organochlorines(e.g. PCB, PCDF, PCDD), PAHs, carbonyl compounds, fuels, chlorinatedsolvent, or other such materials.

More specific embodiments of the invention include those wherein theporous medium is functionalized with the following adsorptionmodifier(s) and exhibits enhanced affinity for respective organicvolatile compounds included in the following table:

Adsorption modifier Enhanced affinity towards the following class(es) ofvolatile organic compound(s) Biphenyl group FuelsMethoxytriethylenoxypropyl- Chlorinated solvents, carbonyl groupcompounds

Another aspect of the invention provides a method of capturing one ormore volatile organic compounds (VOC) or semi-volatile organic compounds(SVOC) from a gaseous atmosphere, the method comprising:

-   exposing a mesoporous silica of the MCM-41 type (hexagonal) to an    atmosphere comprising the one or more VOC and/or one or more SVOC,    thereby capturing the one or more VOC and/or one or more SVOC.

Embodiments of the method include those wherein: a) the gaseousatmosphere is at ambient pressure and temperature; b) the gaseousatmosphere is at about 20-50° C. and about 265-1080 mbar; c) themesoporous silica is non-functionalized; d) the mesoporous silica isfunctionalized; e) the mesoporous silica comprises non-functionalizedmesoporous silica and one or more functionalized mesoporous silicas; f)the mesoporous silica is a silane functionalized mesoporous silica; g)the mesoporous silica is a defined herein.

In some embodiments, the invention provides a method of providing pluralsamples of sorbent differing in exposure time limit, the methodcomprising:

-   providing a device comprising plural separate sections of sorbent,    each section in a respective sealed receptacle;-   unsealing a first receptacle comprising a first section of sorbent,    exposing said first section to VOC or SVOC for a first period of    time, and then sealing the first receptacle;-   unsealing a second receptacle comprising a second section of    sorbent, exposing said second section to VOC or SVOC for a second    period of time, and then sealing the second receptacle; wherein-   the first and second receptacles can be unsealed at the same or    different times.

Embodiments of the invention include those wherein: a) the first andsecond receptacles are separately (independently) sealable; b) the firstand second receptacles are separately (independently) unsealable; c) thefirst period of time is different than the second period of time; d) thefirst time period is the same as the second time period; e) bothreceptacles are unsealed at the same time; f) both receptacles aresealed at the same time; g) the receptacles are unsealed at differenttimes; h) the receptacles are sealed at different times; i) the firstperiod of time is less than the second period of time; j) the firstperiod of time is greater than the first period of time; or k) acombination of any two or more thereof.

Another aspect of the inventions provides a method of training an animalto sense one or more VOC or SVOC, the method comprising:

-   exposing a mesoporous silica of the MCM-41 type (hexagonal) to an    atmosphere comprising the one or more VOC and/or one or more SVOC,    thereby forming a compound-containing mesoporous silica; and-   exposing the animal to the compound-containing mesoporous silica.

Embodiments of the method include those wherein the method furthercomprises one or more of the following steps: a) hiding thecompound-containing mesoporous silica before exposing the animal to it;b) placing the compound-containing mesoporous silica away from theanimal; c) allowing the animal to search for the compound-containingmesoporous silica; d) rewarding the animal after it finds thecompound-containing mesoporous silica.

The method of training is particularly suitable for trainingbomb-sniffing or drug-sniffing animals, particular those used by thearmed services or law enforcement.

The sorbent and devices of the invention are also suitable for use ascontrol or test samples in security screening procedures that employdevices that sense illegal or dangerous VOC or SVOC.

The invention includes all combinations of the embodiments,sub-embodiments and aspects disclosed herein. Accordingly, the inventionincludes the embodiments and aspects specifically disclosed, broadlydisclosed, or narrowly disclosed herein, as well as combinations thereofand subcombinations of the individual elements of said embodiments andaspects.

Other features, advantages and embodiments of the invention will becomeapparent to those skilled in the art by the following description,accompanying examples.

BRIEF DESCRIPTION OF THE FIGURES

The following figures form part of the present description and describeexemplary embodiments of the claimed invention. These drawings are notnecessarily drawn to scale and are instead intended to illustrate thegeneral principles of the invention as further described herein.Although specific embodiments are described below with specificreference to the drawings provided, other embodiments are possiblewithout deviating from the spirit and scope of the present invention.The skilled artisan will, in light of these figures and the descriptionherein, be able to practice the invention without undue experimentation.

FIG. 1A depicts a generalized drawing of the structure of the mesoporoussilica of the invention.

FIG. 1B depicts a TEM (transmission electron microscope) image of an endview of a mesoporous silica particle.

FIGS. 2A and 2B depict exemplary BET nitrogen adsorption-desorptionisotherms for the non-functionalized (FIG. 2A) andmethoxytriethylenoxypropyl-functionalized (MP-functionalized) mesoporoussilica (FIG. 2B).

FIG. 3 depicts pore size (radius measured in Angstroms) distributions ofthe functionalized and non-functionalized sorbents analyzed using theBJH model.

FIGS. 4A and 4B depict charts summarizing the measured uptake capacitiesand the maximum desorption temperature for the target analytes (VOC orSVOC) from the surface of the improved non-functionalized mesoporoussilica MCM-41 type of the invention. Analyte uptake capacities andmaximum desorption temperatures determined for non-functionalizedXploSafe sorbent and select target analytes (VOC or SVOC) are provided.

FIG. 5 depicts an exemplary thermograph for desorption of benzene fromvarious different sorbents.

FIG. 6A depicts a top plan view of a device comprising plural uniformsections of sorbent on a surface.

FIG. 6B depicts a perspective of an alternative device comprising pluraldifferent sections of sorbent on a surface.

FIG. 7 depicts a chart summarizing the relative mass changes measuredfor sorbate (compound) loaded sorbent samples and non-functionalizedOSU-6 sorbents after 18 weeks of storage at +24° C.

FIG. 8 depicts an exploded view of an alternative device of theinvention.

FIG. 9A depicts a top plan view of the device of FIG. 8.

FIG. 9B depicts a cross-sectional side elevation view of the device ofFIG. 9A along sectional view line A-A.

FIG. 10 depicts an exploded view of a device of an alternative device ofthe invention.

FIG. 11A depicts a top plan view of the device of FIG. 10.

FIG. 11B depicts a cross-sectional side elevation view of the device ofFIG. 11A along sectional view line B-B.

FIG. 12 depicts a perspective view of an alternative device of theinvention.

FIGS. 13A-13C depict perspective views of some of the components of thedevice of FIG. 12.

FIG. 14 depicts a perspective view of a partially disassembled alternatedevice of the invention.

FIGS. 15A and 15B depict a perspective view of an alternative device ofthe invention assembled in two different arrangements.

FIG. 16 depicts an exploded perspective view of the device of FIG. 15B.

FIG. 17 depicts an exploded perspective view of an alternative device ofthe invention.

FIG. 18 depicts an exploded perspective view of an alternative device ofthe invention.

FIG. 19 depicts an exploded view of an alternate device of theinvention.

FIGS. 20A and 20B depict exemplary FTIR spectra for (1) pure OSU-6, (2)methoxytriethylenoxypropyl-functionalized OSU-6, (3)biphenyl-functionalized OSU-6, and (4) octyl-functionalized OSU-6powders.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides improved silica-based sorbent(s) and use(s)thereof and devices containing the same.

The sorbent and devices of the invention provide numerous improvementsover known sorbents and devices: a) improved sampling rates; b) improvedstabilization and retention of VOC or SVOC during storage and handlingat temperatures ranging from −20° C. to 35° C.; c) reduced degradationand/or desorption of VOC or SVOC; d) ability to conduct two differentexposure tests with the same device; e) reduced or no organiccontribution from sorbent during thermal desorption analysis; f) abilityto conduct analysis by two different methods, e.g. solvent extractionand thermal desorption, using sorbent from the same device; g)quantifiable analyte (VOC or SVOC) recovery of at least 90% for mostcompounds; h) low limits of quantitation; i) low limits of detection;and/or j) improved rate of adsorption of VOC or SVOC as compared toother sorbents.

As used herein, the term “OSU-6” is taken to mean non-functionalizedmesoporous silica, the term “MP-OSU-6” is taken to meanmethoxytriethylenoxypropyl-functionalized OSU-6, the term “OT-OSU-6” istaken to mean octyl-functionalized OSU-6, and the term “BP-OSU-6” istaken to mean biphenyl-functionalized OSU-6.

As used herein, the term “non-functionalized mesoporous silica” (or“non-functionalized sorbent”) refers to mesoporous silica that has notbeen functionalized with one or adsorption modifiers.

As used herein, the term “sorbate” refers to VOC or SVOC captured by (oradsorbed by) the sorbent.

The mesoporous silica of the MCM-41 (hexagonal tubular pores structure)types exhibits a tertiary or quaternary structure characterized bystacked layers of hexagonally-shaped parallel tubes. FIG. 1 depicts ageneralized rendition of its structure.

Embodiments of the invention include those wherein the porous medium isan improved grade of MCM-41 type mesoporous silica that possesses one ormore, and preferably a combination of two or more, of the followingproperties:

Property Minimum value Range of values Linear formula SiO₂ polymer Formpowder Pore structure Hexagonal tubes Pore size (diameter) >2 nm about 2to about 30 nm about 2 to about 15 nm about 5 to about 10 nm averageabout 8 nm Pore volume >0.5 cm³/g about 0.5 to about 2.0 cm³/g about 1.0to about 2.0 cm³/g about 1.2 to about 1.7 cm³/g average about 0.5-0.7ml/g Surface area at least 600 m²/g about 600 to about 1000 m²/g and upto 900 m²/g about 700 to about 1000 m²/g about 800 to about 1000 m²/ggreater than about 700 m²/g Channel wall >2 nm about 2 to about 5 nmthickness about 2 to about 4 nm about 2 to about 3 nm

The grade of MCM-41 mesoporous silica of the invention exhibits a largepore size, a high pore volume, and, when compared to conventional gradesof MCM-41, exhibits thicker channel walls, higher thermal stability (upto 950° C.), and higher hydrothermal stability (which is expressed interms of changes to sorbent porosity after treatment in boiling waterfor more than 25 hours. In some embodiments, the mesoporous silica ofthe invention exhibits no, or less than 10%, or less than 5% change insorbent porosity after treatment in boiling water for more than 25hours.

Preferred embodiments of the mesoporous silica are prepared according tothe procedure of Example 1.

A generalized procedure for preparation of the mesoporous silica is asfollows. A templating solution is prepared by mixing a templatingmaterial in water and agitating the mixture for form a substantiallyuniform foam or froth, which might appear to be a paste. A silicasolution is formed by mixing tetraalkylorthosilicate in solvent (e.g.alcohol or mixture of alcohols). The templating solution is stirred andan acidic solution is added (incrementally or continuously) to it. Tothat mixture, the silica solution is added while mixing to form aprecursor mixture. Water is then added to the precursor mixture whilelightly mixing and that mixture is left standing for a period of days atroom temperature. The mesoporous silicate is then separated from thesupernatant and washed with water and then ethanol. A more detaileddescription for preparation of the mesoporous silica is provided inExample 1.

X-ray diffraction analysis of the OSU-6 depicts three well-resolveddiffraction peaks in the region of 2Θ=1-5°, which can be indexed to the(100), (110) and (200) diffractions, characteristic of the formation ofwell-arranged hexagonal mesostructures.

The SEM (scanning electron microscopy) image of the OSU-6 shows a narrowparticle size distribution and well defined spherical particles. Theparticle size of the OSU-6 was in the range of about 250 nm to about1500 nm.

The TEM (transmission electron microscopy) image of the OSU-6 shows thepresence of well-defined pore channels with diameters of about 5 nm(about 2 to about 30 nm) and wall thickness of about 2 nm about 1 toabout 5 nm).

FIGS. 2A and 2B depict exemplary BET nitrogen adsorption-desorptionisotherms for the non-functionalized (FIG. 2A) andmethoxytriethylenoxypropyl-functionalized (MP-functionalized) mesoporoussilica (FIG. 2B). Adsorption/desorption isotherms are used tocharacterize the surface area, pore volume, and pore size distributionsof the sorbent. The non-functionalized sorbent (FIG. 2A) contains typeIV isotherms, which are associated with the capillary condensation ofadsorbate into mesopores, while the observed hysteresis of type Aindicates that OSU-6 pores have cylindrical shapes. Afterfunctionalization (FIG. 2B), the hysteresis disappears, and theadsorption-desorption isotherms assumed the shapes of type II isothermsdue to the attachment of functional groups to the pore walls.

The mesoporous silica can be non-functionalized or functionalized. Insome embodiments, the porous medium, such as mesoporous silica, isfunctionalized with one or more adsorption modifier functional groupsthat enhance the binding of a VOC or SVOC. For example, the mesoporoussilica is functionalized by treating it with a trialkoxyalkylsilane(R¹Si(OR²)₃), wherein:

-   R¹ is selected from the group consisting of aromatic group, alkyl    group, oxygen-containing alkyl groups, sulfur-containing alkyl    groups, nitrogen-containing alkyl groups, phenyl, biphenyl,    (C1-C8)-alkyl, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,    octyl, methoxytriethyleneoxypropyl, alkoxyalkyleneoxyalkyl,    haloalkyl, halo-(C1-C8)-alkyl, aminoalkyl, alkoxyalkyl,    polyaromatic, toluyl, fluoroalkyls, fluroaromatics, and their    combinations; and-   R² is selected from the group consisting of alkyl, C1-C12-alkyl,    with methyl, ethyl, and propyl being preferred, thereby forming a    silane-functionalized mesoporous silica comprising plural silane    groups R¹Si— covalently bound to oxygen molecules of the mesoporous    silica.

Exemplary trialkoxy silanes include:

Such a silane-functionalized mesoporous silica generally has thefollowing chemical formula: silica-O—Si(R¹)(OR²)_(n)—O_(m)—; wherein nis 0, 1 or 2, and m is 2, 1, or 0, respectively. Functionalization ofthe mesoporous silica converts the silicon oxide/hydroxide surfacewithin the pores of the mesoporous silica into the desired derivativesby formation of an organosilsequioxane polymer grafted to the surface ofthe silica.

Its high surface area allows the sorbent to uptake relatively largeamounts of VOC and SVOC. The sorbent exhibits exceptional adsorptioncapacity, rate of capture and a high propensity to stabilize evencompounds such as acetaldehyde and methylene chloride. After adsorptionof VOC or SVOC, the sorbent can be introduced directly into the samplechamber of an analytical instrument, e.g. gas chromatograph and/or massspectrometer, if desired, for rapid quantitation and/or identificationof the adsorbed VOC or SVOC. In some embodiments, the sorbent retains anadsorbed VOC or SVOC even after exposure of a VOC-containing orSVOC-containing sorbent to a temperature of up to about 50° C. for aperiod of up to about a week (which was observed for compounds withrelatively high maximum desorption temperatures such as1,2,4-trimethylbenzene and naphthalene).

Functionalized mesoporous silica can be made according to the followinggeneralized procedure. Non-functionalized mesoporous silica is renderedanhydrous by removal of substantially all moisture, such as byazeotropic distillation and/or desiccation with or without heat and atatmospheric or reduced pressure. For example, the mesoporous silica isrefluxed in dry organic liquid under dry atmosphere to remove moisture.The organic liquid is removed from the mesoporous silica by drying underheat at reduced pressure. The dried mesoporous silica is suspended inorganic liquid and treated with triethanolamine (TEA) at roomtemperature to form TEA-mesoporous silica (TEA-MS). The TEA-MS solidsare then separated from the supernatant. The recovered TEA-MS solids arewashed with dry organic liquid, and optionally vacuum-dried. The TEA-MSis suspended in organic liquid and treated with functionalizing agentwhile heating and mixing. The functionalized mesoporous silica (MS) isseparated from the supernatant and washed with organic liquid.Functionalization was performed according to Example 2.

Functionalized sorbent may exhibit different performance properties thannon-functionalized sorbent. Example 9 describes the results of a studycomparing the uptake capacities and uptake rates for four differentsorbents. The data indicate that the uptake capacity of the sorbentdecreases with surface functionalization which is mainly due to reducedsurface area; however, an advantageous increase in the rate of uptakefor specific target compounds was observed for the functionalizedmesoporous silica.

The sorbent can comprise (or consist essentially of or consist of)non-functionalized sorbent, functionalized sorbent, or a combination(mixture) of non-functionalized sorbent and functionalized sorbent. Insome embodiments, the sorbent comprises non-functionalized mesoporoussilica, functionalized mesoporous silica, or a mixture ofnon-functionalized mesoporous silica and one or more functionalizedmesoporous silicas. In some embodiments, non-functionalized sorbentcomprises the majority of the mixture. In some embodiments,functionalized sorbent comprises the majority of the mixture. In someembodiments, non-functionalized sorbent and functionalized sorbent arepresent at about the same amount.

The weight ratio of non-functionalized sorbent to functionalized sorbentcan range from about 1:100 to about 100:1 with all integer andfractional values therein being contemplated. In some embodiments, theratio ranges from about 80:20 to about 20:80, about 70:30 to about30:70, about 60:40 to about 40:60, about 80:20 to about 40:60, about80:20, about 95:5, about 90:10, about 70:30, about 60:40, about 50:50,about 40:60, about 30:70, about 20:80, about 90:10, or about 95:5.

Exemplary suitable ranges for the weight percentage of the differenttypes in the mixture can be as follows, wherein the sum total of theweight percentages is 100%.

Non-functionalized 1^(st) Functionalized 2^(nd) Functionalized sorbentsorbent sorbent (% wt) (% wt) (% wt) 100 0 0 about 80 or less up toabout 10 10  about 75 or less up to about 15 up to about 10 about 50 orless up to about 30 up to about 20 about 5 to less up to about 95 0 than100 up to about 95 about 5 to less 0 than 100 ^(a)about 5 to less lessthan about 95 less than about 95 than 100 ^(b)less than about 95 about 5to less less than about 95 than about 100 ^(a)wherein the total of1^(st) and 2^(nd) functionalized sorbent is up to 95% wt. ^(b)whereinthe total of non-functionalized and 1^(st) functionalized sorbent is upto 95% wt.

Mixtures of non-functionalized mesoporous silica and one or morefunctionalized mesoporous silicas can be made according to Example 4,whereby two or more different types of mesoporous silica are mixedtogether. Such mixtures may exhibit different affinity (loadingcapacity) for the sorbate.

Example 9 provides a comparison of the uptake capacity for variousmixtures of sorbent. As the sorbent is functionalized, the maximumuptake capacity decreases; however, the rate of capture is notnecessarily decreased. In some embodiments, the functionalized sorbentof the invention exhibits increased uptake rate, slower rate ofdesorption, and decreased maximum uptake capacity as compared to thenative non-functionalized sorbent.

The sorbent can be provided in compressed, non-compressed, pellet,tablet, beads, loose powder, bound powder, powder enclosed in porouscontainer, powder in sachet or bag, thin film. The sorbent may or maynot be affixed (attached, bound) to a substrate.

The invention also provides a method of adhering sorbent to a substrate,the method comprising: a) suspending the sorbent in organic liquid toform a suspension; b) depositing the suspension to a substrate; and c)removing the organic liquid, thereby leaving the sorbent adhered ontothe substrate. In some embodiments, the substrate comprises silica,silicate or inorganic crystal. The substrate can be activated by heatand/or chemical prior to adherence of the sorbent.

Materials suitable for making substrates to which the sorbent is affixedinclude glass fibers and monoliths, plastic fibers and monoliths, fabricthreads and woven fibers, paper, and metal fibers and monoliths withfluoropolymer (e.g PTFE) or glass fibers and monoliths being preferred.Such material will generally be inert and will not adsorb or capture VOCor SVOC.

The porous medium can adsorb many different types of compounds,including but not limited to: aromatic hydrocarbon, non-aromatichydrocarbon, alkylhalide, alkylaldehyde, polar organic compound,non-polar organic compound, explosive, narcotic, controlled substance,illegal substance, industrial chemical, commodity chemical, pesticide,herbicide, poison, solvent, or other material.

Exemplary explosives include, by way of example and without limitation,PETN (pentaerythritol tetranitrate), RDX(1,3,5-trinitro-1,3,5-triazinane), TNT (2,4,6-trinitrotoluene), TATP(triacetone triperoxide; tricyclic acetone peroxide), HMTD(hexamethylene triperoxide diamine;3,4,8,9,12,13-Hexaoxa-1,6-diazabicyclo[4.4.4]tetradecane) or others.

Exemplary narcotics, controlled substances, or illegal substancesinclude, by way of example and without limitation, Schedule I ControlledSubstances such as heroin, LSD, marijuana, peyote, and ecstasy, ScheduleII Controlled Substances such as Dilaudid, methadone, Demerol,OxyContin, Percocet, morphine, opium, codeine, amphetamine (Dexedrine,Adderall), and methamphetamine Schedule III Controlled Substances suchas Vicodin, Codeine, Suboxone, ketamine, and anabolic steroids. ScheduleIV Controlled Substances include Xanax, Soma, Klonopin, Valium, Ativan,Versed, Restoril, Halcion or others.

Exemplary industrial or commodity compounds include, by way of exampleand without limitation, solvent(s), 1,1,2,2-tetrachloroethane, Aceticacid, Acetone, Aroclor 1221, Benzylchloride, Carbon tetrachloride,Chlorobenzene, Chloroform, Chloropyrifos, Chrysene, Decalin,Dibenzofuran, Diethyl Ether, Ethanol, Ethylene oxide, Formic acid,Glutaraldehyde, Halothane, Hexadecane, Isoflurane, Isopropanol, Lindane,Malathion, Methanol, Methyl ethyl ketone, Methyl methacrylate,Naphthalene, Nitromethane, O-phthalaldehyde, PCB-209, Pyrene, Pyridine,Resmethrin, Styrene, Tetrahydrofuran (THF), Xylene (+Toluene), Aniline,Bifenthrin, Bisphenol A, Chloroxylenol, Cidex (O-phtalaldehyde),Desflurane, Dibutyl phthalate, Ethylbenzene, Hexachlorobenzene, Lindane,Perchloroethylene, Pyrene, Tricresylphosphate, 1,2,4-Trimethylbenzene,Acetaldehyde, Acrolein, Benzene, Hexane, Methylene Chloride, Napthalene,Vinyl Acetate, Xylene, 1,2,3,4-tetrazole, 5-aminotetrazole, Dichlorovos,Octane, PCB 209, Permethrin, RDX, TNT, Trichloroethylene,1,1,2-trichloroethane, 1,2,-dichlorotetrafluoroethane, acetaldehyde,acetone, acetonitrile, Acrolein, acrylonitrile, crotonaldehyde, ethylalcohol, formaldehyde, freons, isopropyl alcohol, methyl ethyl ketone,methyl isobutyl ketone, methylene chloride, Mono Ethyl Amine, NitrogenDioxide, Ozone, polychlorinated biphenyls.

The uptake or loading capacity of the sorbent of the invention for VOCor SVOC was evaluated. FIGS. 4A and 4B depict charts summarizing themeasured uptake capacities and the maximum desorption temperature forthe target analytes (VOC or SVOC) from the surface of non-functionalizedmesoporous silica (NFMS) of the invention. NFMS exhibits a highdesorption temperature for aromatic hydrocarbons, such as naphthalene,xylene and 1,2,4-trimethylbenzene, and it exhibits a high uptakecapacity for aldehydes, such as acetaldehyde. For the majority of targetcompounds with medium and high vapor pressure, the NFMS of the inventionis able to uptake (capture, adsorb) at least about 1-fold its weight ofVOC or SVOC.

The uptake capacities were obtained for a wide range of compounds on thesurface of the functionalized OSU-6 sorbent. For all the studiedcompounds, the uptake capacities for the functionalized sorbents wereslightly lower than those obtained for non-functionalized OSU-6 (mainlydue to the reduction of the sorbent surface area afterfunctionalization); however, the related adsorption rates were higherfor the majority of the studied compounds, because of the possiblechemical interactions between sorbate species and the surface functionalgroups. This effect was more pronounced for volatile compounds withrelatively high vapor pressures such as methylene chloride,acetaldehyde, and hexane. For example, for hexane the rate constantvalue increased from 0.070 h⁻¹ (for non-functionalized OSU-6) to 0.092h⁻¹ (for octyl-functionalized OSU-6) and to 0.11 h¹ (forbiphenyl-functionalized OSU-6) since the non-polar hexane chainsinteract more actively with the non-polar biphenyl- and octyl-functionalgroups than with the non-functionalized OSU-6 surface.

Performance of the mesoporous silica of the invention was compared toliterature reported values for uptake capacity of activated carbon. Theresults are depicted in the table below.

XploSafe Activated sorbent uptake carbon uptake capacity capacity Target(mg/mg (mg/mg # Class compound sorbent) sorbent)** 1 PolynuclearNaphthalene  0.221 ± 0.006* >0.056 Hydrocarbons (PAHs) 2 Carbonyl Vinylacetate 1.34 ± 0.02 0.02 Compounds 3 Fuels Hexane 0.94 ± 0.01 0.053Octane  0.98 ± 0.05* 0.056 Xylene 1.216 ± 0.008 >0.056 Benzene 1.268 ±0.006 0.049 4 Chlorinated Trichloro- 2.10 ± 0.01 >0.056 solventsethylene *Measured for 6-mm sorbent pellets ***Estimated using the datafrom literature (https.//www.assaytech.com/sampling-guide).

Accordingly, the sorbent of the invention, and devices containing it,substantially outperform activated carbon as a sorbent.

Knowledge of the desorption temperature of particular VOC or SVOC fromthe sorbent can be used to develop proper storage conditions forsorbents loaded with the respective compound(s). FIG. 5 depicts anexemplary thermograph for desorption of benzene from various differentsorbents. The data were obtained according to Example 7. FIGS. 4A and 4Bdepict charts summarizing the observed maximum desorption temperaturefor the target analytes (VOC or SVOC) from the surface of the improvednon-functionalized mesoporous silica MCM-41 type of the invention. Abovethe desorption temperature, the sorbate is thermally desorbed from thesorbent as evidenced by the decrease in sorbent weight and constantsorbent weight as the temperature increases.

The data indicate that the majority of the studied analytes are retainedat the sorbent surface at temperatures below about 40° C., below about45° C., or below about 50° C. In addition, the physical adsorptionenergy for the target compounds inside the pores appears to correlatewith their vapor pressure since the analytes with relatively low vaporpressures (for example, xylene, 1,2,4-trimethylbenzene, and naphthalene)desorb from the non-functionalized and functionalized sorbates at muchhigher temperatures.

The sorbent employed in the invention comprises a porous medium thatcaptures and stabilizes VOC and SVOC sorbate under ambient conditionsand exhibits a desorption temperature of about 50° C. or higher for theVOC or SVOC. Example 10 provides the experimental procedure for samplingrate analysis. 15-Min and 8-hour exposure of target compounds at OSHApersonal exposure limits (PEL) were obtained for sorbent. Effectivesampling rates were obtained at 1/10^(th) and 10-fold OSHA PEL. Thesorbent and devices of the invention provide equivalent or improvedsampling rates as compared to reported literature on known devices. Inpreferred embodiments, the sorbent and devices of the invention providesampling rates as described herein.

In view of the desorption temperature data, we conclude that RT storage(below 30° C.) and long storage times are possible. This is consistentwith experimental studies.

By way of example, two dosimeters prototypes (clip-on flat badge formand vertical tubular badge form) were designed and 3D-printed. Thedosimeters were modeled with 3D CAD software in order to rapidlygenerate workable prototypes that were used to perform “field tests”.

FIG. 6A depicts a device (1) comprising plural sections (2 a-2 d) ofsorbent on a substrate (3). Each section comprises about the same amountof sorbent.

FIG. 6B depicts a device (5) comprising plural sections (6-9) of sorbenton a substrate (4). Two or more of the sections comprise differentamounts of sorbent.

The sectioned devices (1, 5) can be used to provide plural sorbentsamples having the same exposure to (content of) VOC or SVOC. Inpreferred embodiments, the device comprises 2-4 sections of sorbent.Such a device allows a user to obtain samples for different exposuretime limits from a single device, e.g. one or more of the sectionsundergo exposure according to a first period having a first time limit,and one or more of the sections undergo a exposure according to a secondperiod having a different second time limit. For example, one or moresection can undergo a 15-min time limit exposure, one or more sectionscan undergo an 8-hr time limit exposure. Moreover, a device havingplural sections of sorbent can provide samples that can be analyzed bydifferent techniques.

The dosimeter (10) of FIGS. 8, 9A and 9B is a clip-on style badgedosimeter comprising a removable impermeable membrane or cover (11), cap(12) with port, diffuser (13) with ports, o-ring (14), protective meshcover (15), retainer ring (16), body (17). The body comprises plural oneor more cavity (18) for placement of sorbent. In this particularembodiment, the cap is engaged to the body threaded engagement means;however, any other means are suitable, e.g. snap-fit, threaded. Thedosimeter optionally further comprises mounting means for attaching thedosimeter to another object during use or storage.

The body can be molded from a non-reactive polymer and covered with apermeable cavity covering to facilitate replacement and subsequentanalysis of the exposed sorbent. Thus, users can simply replace theutilized sorbent cavity with a fresh adsorbent pack and reuse the restof the badge. The sorbent is secured inside the badge by using an o-ring(suitable material is Viton®) (blend of synthetic rubber andfluoropolymer elastomer), which minimizes exposure of the sorbent.Undesired exposure of the sorbent is achieved using a removableimpermeable cap covering, e.g. a sheet made from fluorinated plasticsheets such as Kynar® PVDF or Tedlar® PFA. The easy-to-peel cap coveringcan be secured with adhesive or can be sonically welded to the cap.Three prototype clip-on badges (with dimensions of 55.0×35.6×14.6 mm)for initial testing were printed using laser-sintered nylon provided byShapeways.

The sorbent material cavity, housing thickness, and exposure aperturecould be optimized to facilitate maximum vapor exposure (diffusion)during use and to prevent vapor loss (effusion) during storage and whileen route for analysis.

Field tests were conducted according to Example 1 on dosimeter badgesprototypes of FIGS. 8 and 14 by exposing them to vanillin vapors. Thevapors originated from four open containers of 3″ in diameter thatcontained 2 g of pure vanillin powder placed inside an office room withdimensions of 15′×17′×7.5′. Two different experiments were conducted for15 min and 8 h, corresponding to the standard short-term and long-termOSHA exposures. The maximum vanillin concentration in air correspondingto that of its saturated vapor is very low and is equal to 0.16 ppm. Thesorbent from the dosimeter badge exposed to vanillin was analyzed by amass spectrometer.

The dosimeter exposed to the air containing vanillin vapor for 8 hoursexhibited two characteristic mass spectrometry peaks at m/z=151 and 152with the peak ratio identical to that of pure vanillin vapor. While thedosimeter exposed for 15 minutes recorded significantly lower amounts ofvanillin vapor, it is consistent with the very low pressure of vanillinvapor at room temperature. For sorbent sample exposed to vanillin vaporfor 8 hours, the adsorbed vanillin content measured was below 0.5 μg,which corresponds to the estimated sampling rate of around 1 mL/min.This value was very close to the magnitudes obtained for other targetcompounds with low vapor pressures (for example 1,2,4-trimethylbenzeneand xylene), indicating the technical feasibility of the dosimeter'sapplication to provide exposure-monitoring data for long-term monitoringof non-volatile compounds with extremely low vapor pressures.

To capture the widest range of analytes based on their vaporconcentrations in air (volatile versus non-volatile compounds), thesorbent surface exposure in a dosimeter can be adjusted. For example, inlonger exposures to target compounds with relatively high vaporpressures, the exposed area should be minimized in order to preventearly sorbent saturation, while at shorter exposure durations(especially for analytes with low vapor pressures), the exposed sorbentarea should be as high as possible. This can be achieved by varying thenumber of exposure ports/slits in the dosimeter cover, effectivelyvarying the exposed fraction of the sorbate to the environment bycontrolling the number of port open.

The device (25) of FIG. 10 is an alternate embodiment of the dosimeter,which is of a circular badge format. It comprises a body (30) having atone or more cavities (31), each of which is adapted to retain sorbent ora substrate comprising sorbent. The body can comprise a partial cover(32) for the cavity. The dosimeter further comprises a diffuser (27)engaged to the body. The diffuser comprises plural ports havingmesh-type or lattice-type coverings (28, which may or may not beintegral with the cap). The dosimeter further comprises a cover (26)engaged with the cap and slidable in relation to the cap, whereby it canbe moved to cover or uncover one or more ports of the cap. The covercomprises one more ports (26 b) and one or more lids (26 a). The portsprovide exposure of the diffuser to the atmosphere and the lids blockexposure of the diffuser to the atmosphere.

The sorbent can be placed in the cavity in any form desired, but if itis included as a powder, then the ports of the cap will comprise aporous, permeable or perforated cover to help retain the sorbent withinthe cavity(ies). The sorbent can also be placed as a powder in a sachetor porous bag, in which case the covering of the ports is optional. Whenfully assembled and before deployment for use, the cavity(ies) aresealed and isolated from the outer environment, thereby avoidingcontamination of the sorbent. During use, the cover ismoved/slid/rotated, and the sorbent is exposed to the atmosphere. Afteruse, the cover can be used to reseal the badge for storage. As needed,one or more of the portions (sections) of sorbent are then removed fromthe dosimeter and subject to analytical testing for quantitation ofcaptured VOC and SVOC.

FIGS. 11A and 11B depict perspective views of the device (10) of FIG.10. In FIG. 11A, the cover (16) is covering the three ports of the cap(13). In FIG. 11B, the cover has been slid away from the ports, therebyleaving them uncovered and exposed to the atmosphere.

FIG. 12 depicts a perspective view of an alternate dosimeter (40), whichis of a rod/tube or pen/cartridge type format, comprising a hollow bodycover (43) engaged to a capture assembly (41). The dosimeter optionallyfurther comprises a fastener (42 a, e.g. a clip), whereby the dosimetercan be attached to another object during use and/or storage. Thedosimeter optionally further comprises a receptacle (42 b) adapted toreceive a fastener or holder (not shown).

The hollow body cover (43, FIG. 13A) comprises an opening (44) and anoptional pedestal (45). The cover is adapted to receive and removablyretain the capture assembly (41, FIG. 13B) comprising a hollow diffuser(46 a) and a cartridge holder (41 b, FIG. 13C). The diffuser comprisesplural ports (46) and is adapted to receive and removably retain thecartridge-holder (41 b), which comprises plural sorbent-containingcartridges (48 a, 48 b) held in place by a retainer (47) comprisingengagements (49 a, 49 b). When fully assembled and before deployment foruse, the cartridges are sealed and isolated from the outer environment,thereby avoiding contamination of the sorbent in the cartridges. Duringuse, the cover is removed, and the cartridges are exposed to theatmosphere. After use, the cover can be used to reseal the badge forstorage. As needed, one or more of the cartridges are then removed fromthe dosimeter and subject to analytical testing for quantitation ofcaptured VOC and SVOC. FIG. 13B depicts the capture assembly with thecover (43) removed such that the plural ports are visible, therebyexposing the cartridges (48 a, 48 b) to the atmosphere to permit captureof VOC and SVOC. FIG. 13C depicts the cartridge holder (41 b) withdisengaged from the diffuser (41 a) and the cover (43).

FIG. 14 depicts an alternate embodiment (50) of the body/cartridgeformat device of the invention. The device comprises a cover (51) and acartridge-holder (52) within which one or more sorbent-containingcartridges (53) are disposed. The cover is engageable with thecartridge-holder to provide a sealed environment and to isolate thecartridges from the atmosphere of an environment of use. Thecartridge-holder comprises plural ports (54) to permit exposure of thecartridges while at the same time protection of the cartridges. Thisdevice has increased surface area and contains the sorbent in acartridge embedded in a glass-microfiber filter paper. In an alternateembodiment, the cartridge is disengaged from the cartridge-holder andinserted into the cover for containment. The device is assembled byinserting the head (55) of the cartridge holder into a hole (56) at thebase of the cover (51) and so that the head (55) exits the hole (57) atthe head of the cover.

FIGS. 15A and 15B depict alternate assembled arrangements of the device(65) comprising diffuser (68), cartridge holder (69), and covers (66,67). In FIG. 15A, the covers superpose the ports of the diffuser,thereby sealing the interior of the device and avoiding exposure of thesorbent to the environment. In FIG. 15B, the covers superpose the rearof the device, thereby exposing the ports (75, 76 of FIG. 16) of thediffuser and the sorbent to the environment of use. FIG. 16 depicts anexploded view of the assembled device of FIG. 15B. The cover (66)comprises engagements (77) adapted to temporarily engage the cover withbody of the diffuser (68) and/or the cartridge holder (69). The pluralsorbent-containing cartridges (74) are placed in respective pluralreceptacles (72) of the holder (69) and held in place with pluralrespective retainers (73). In an alternate arrangement, the cover (66)superposes the ports (75), and the cover (67) does not superpose theports (76), thereby allowing exposure of sorbent beneath the ports (76)but not of sorbent beneath the ports (75). In a likewise but oppositefashion of yet another an alternate arrangement, the cover (67)superposes the ports (76), and the cover (66) does not superpose theports (75), thereby allowing exposure of sorbent beneath the ports (75)but not of sorbent beneath the ports (76).

As discussed above, a device comprising plural sections (portions) ofsorbent that can be sealed independently of one another can be used toobtain, from a single device, samples having different exposure timelimits.

FIG. 17 depicts an exploded view of an alternate embodiment of a device(80) comprising a two-part cover (81), two-part diffuser (82 a, 82 b),and sorbent holder (83), which comprises plural chambers (receptacles,84) that retain sorbent or substrate comprising sorbent. The chambersoptionally comprise plural ports (85) that are optionally covered withrespective port caps (86). The two-part diffuser (81) comprises an upperportion (82 b) and a lower portion (82 a) each of which superposesrespective receptacles (84) of the holder. The cover (81) comprises anupper portion (81 a) and a lower portion (81 b). During storage, theportions (81 a, 81 b) of the cover superpose and seal respectiveportions (82 b, 82 a) and receptacles (84). During use, one or morereceptacles can be exposed to the environment of use as follows. Theupper portion (81 a) of the cover can be removed, thereby exposing theupper portion (82 b) of the diffuser and its respective receptaclecomprising sorbent therein. Alternatively, the lower portion (81 b) ofthe cover can be removed, thereby exposing the lower portion (82 a) ofthe diffuser and its respective receptacle comprising sorbent therein.Alternatively, both portions of the cover can be removed to expose allreceptacles to the environment of use. During use, one of more of theport caps (86) can be removed from the ports (85) to increase diffusionof air through the device and maximize entrapment of VOC or SVOC.

In order to facilitate sorbent removal for analysis of VOC or SVOCentrapped therein, the diffuser portions (82 a, 82 b) can be removedseparately. In this manner, some portions (sections) of sorbent can beanalyzed while others are retained with the device for storage.

FIG. 18 depicts a pen-type device (90) comprising a cartridge-holder(94), sorbent-containing cartridge (96), diffuser body (91) and movablecover (93). After loading one or more cartridges onto thecartridge-holder, they are together inserted into the diffuser body inthe direction of arrow B. The device optionally comprises a retainer,e.g. clip, for securing the device to a user during use. During storage,the cover (93) covers diffuser ports (92) and prevents exposure of thecartridge(s) to the open atmosphere. During use, the cover (93) is slidin the direction of arrow A, thereby exposing the diffuser ports andcartridge(s) to the environment of use. Removal of the cartridge isachieved by disengaging the cartridge-holder from the diffuser body inthe reverse direction of arrow B.

FIG. 19 depicts an exploded view of another device (100) of theinvention comprising a cap (105), sorbent-holder diffuser (103), andhollow-body cover (101). The sorbent-holder diffuser comprises areceptacle (104) for holding sorbent or sorbent-containing substrate,and it also comprises plural ports whereby the receptacle can be exposedto the exterior. The hollow-body cover receives and temporarily retainsthe diffuser by insertion thereof (along arrow C) into a receptacle(102) of the cover. The cap (105) is independently engageable with thediffuser and the hollow-body cover. For example, two-stage engagementcan be employed, whereby the cap engages the cover with first-stageengagement and engages the diffuser with second-stage engagement.

Sorbent can be employed as loose powder, layer adhered to a substrate,sorbent containing cartridges, or other such forms (tablets, pellets,sachets). Suitable forms, such as a cartridge or tube, containingsorbent can be made by using a porous or gas-permeable material toretain the sorbent. The pores of the material would have to be smallerthan the average particle size of the sorbent but large enough to permitdiffusion of gas from the environment and into the sorb ent.

A particularly useful material is porous PTFE (polytetrafluoroethylene;e.g. Teflon®) tubes for holding non-functionalized OSU-6 sorbent insidethe housing of the injection molded dosimeters. Porous PTFE tubes andsheets including porous PTFE tube from Markel Corporation can be used.Some suitable tubes have a 3.5 mm OD (outer diameter), 3.0 mm ID, (innerdiameter) and mean pore size of about 0.58 microns and maximum pore sizeof 1.98 microns. The sorbent cartridges provide ease of sorbent transferinto the cavities of (0.25″×3.5″) of thermal desorber tubes (forrecovery through thermal desorption) and/or 2 mL GC/MS vials forrecovery through the solvent extraction analysis technique. The ends ofthe PTFE tube can be sealed with plugs or beads.

Sorbent can be easily analyzed for entrapped VOC or SVOC by thermaldesorption using thermogravimetry equipment. The sorbent orsorbent-containing substrate is simply placed in a sealed container andheated to a temperature above the desorption temperature of the targetanalyte (VOC or SVOC). An aliquot of the headspace of the container isthen obtained and injected into a gas chromatograph. Alternatively, thesealed container is conductively engaged with the injection chamber ofthe gas chromatograph where, upon heating of the container andcartridge, a sample of the headspace of the container is obtained andanalyzed. In some embodiments, the container is sealed with a septum.

In some embodiments, a device of the invention includes ports (vents)that are fully or partially opened or are adjustable as to extent ofopening to optimize the sampling rate for the nature of the targetanalytes and the workplace. Workplaces with volatile organics mayrequire small openings, while workers using relatively non-volatilematerials or material in low concentration (i.e. regents, pesticides)will require larger openings to optimize the absorption and analysis.

The device of the invention can be used for, among other things: a)Operational testing to monitor personal levels to chemicals in andaround natural gas plants, oil refineries and fueling operations; b)Operational testing to monitor personal exposure levels in and aroundmultiple industrial operations to include construction (facilitiesmanagement, air conditioning and refrigeration systems maintenance),health sciences (nursing and healthcare technicians), manufacturing(metal fabrication, machining, welding), and transportation anddistribution logistics (automotive, diesel, pipeline etc.); c)Operational testing on tarmac to measure person exposure levelmonitoring in and around airport operations; d) to monitor personalexposure levels in and around demolition site, site grading, soilstabilization site, and concrete or asphalt paving site; e)field-testing for exposure to pesticides; f) investigate the monitoringof target compounds such as polycyclic aromatic hydrocarbons (PAHs),volatile organic compounds, and toxic organic halogenated dioxins andfurans from burn pits without contaminating the environment or exposingpeople to the toxins; or g) combinations or two or more thereof.

The ability to uptake and stabilize VOC and SVOC allows for prolongedstorage conducive to maintaining a repository of samples for futureanalysis. The sorbent exhibits exceptional adsorption capacity, rate ofcapture and a high propensity to stabilize even compounds such asacetaldehyde and methylene chloride. After adsorption of VOC or SVOC,the sorbent can be introduced directly into the sample chamber of ananalytical instrument, e.g. gas chromatograph and/oror massspectrometer, if desired, for rapid quantitation and/or identificationof the adsorbed VOC or SVOC. In some embodiments, the sorbent retains anadsorbed VOC or SVOC even after exposure of a VOC-containing orSVOC-containing sorbent to a temperature of up to about 50° C. for aperiod of up to about 7 days.

FIG. 7 depicts a chart summarizing the relative mass changes measuredfor sorbate (compound) loaded sorbent samples and non-functionalizedOSU-6 sorbents after 14 weeks of storage at +24° C. Negative valuesindicate mass gains caused by the moisture adsorption on the sorbentsurface. Majority of the exposed sorbent samples retained over 80% ofthe adsorbed sorbate (captured analyte) over 18 weeks. Little to nocompound (sorbate) was lost from the sorbent upon extended storage atroom temperature (about 24° C.) and ambient pressure over a period of 14weeks, when the data was normalized for variation due to moisturesorption/desorption.

Once the badge is closed, the sorbent exhibits a high retention of theVOC and SVOC sorbate after capture thereof, meaning that little to noneof the VOC or SVOC sorbate is desorbed from the sorbent during storageat room temperature. In some embodiments, the sorbate loses less thanabout 25%, less than about 20%, less than about 15%, less than about10%, less than about 5%, less than about 2.5%, or less than about 1% ofits initial mass during storage.

The sorbent stabilizes the VOC and SVOC sorbate against chemicaldegradation during storage. In some embodiments, the sorbate undergoesless than 5% or its initial mass due to chemical degradation duringstorage at room temperature (+24° C.) or in the refrigerator (+6° C.).

The exemplary embodiments herein should not be considered exhaustive,but merely illustrative of only a few of the many embodimentscontemplated by the present invention.

Unless otherwise specified, values indicated herein should be understoodas being limited by the term “about”. As used herein, the term “about”is taken to mean a value that is within ±10%, ±5% or ±1% of theindicated value. For example, “about 6” is taken to mean 6±10%, 6±5% or6±1%.

The entire disclosures of all documents cited herein are herebyincorporated by reference in their entirety.

EXAMPLES

The following materials and procedures are used to prepare exemplaryembodiments of the invention and to demonstrate exemplary uses thereof.

Non-functionalized OSU-6 and the functionalized OSU-6 sorbents disclosedherein are products of XPLOSAFE, LLC (Stillwater, Okla.).

EXAMPLE 1 Preparation of Improved Non-Functionalized Mesoporous SilicaMCM-41 Type

The mesoporous silica of the invention was prepared according to amodified method of Apblett et al. (“Preparation of mesoporous silicawith grafted chelating agents for uptake of metal ions” in ChemicalEngineering Journal (2009), 155(3), 916-9240) or AlOthman et al.(“Synthesis and characterization of a hexagonal mesoporous silica withenhanced thermal and hydrothermal stabilities”, in Applied SurfaceScience (2010), 256, 3573-3580), the entire disclosure of which ishereby incorporated by reference.

A templating solution was prepared first by dissolving 284.0 g (1.08mol) of 1-hexadecylamine (HDA) in 1040 mL of distilled water at roomtemperature, sonicating for 5-10 min to produce foamy and uniform paste.A second solution was prepared by mixing 524 g (2.4 moles) oftetraethylorthosilicate, 448 mL (0.96 moles) of ethanol and 96 mL (1.6moles) of isopropanol in under magnetic stirring at room temperature forabout 45 min. The first solution was stirred for 40 min followed by theaddition of 1000 mL of 1.0 M HCl solution in increments over 10-15minutes and then the second solution in a three-necked round-bottomflask. After 5 min of stirring, 148 mL (1.2 moles) of auxiliary organicmesitylene was added to the reaction mixture, which was then stirred foran additional 25 min. After that, the stirring was stopped, and 1600 mLof distilled water was added to the mixture, which was swirled to mixand then left to age for 7 days at room temperature. The resulting solidwas recovered by filtration, washed with distilled water and ethanol(three times) using a fine filter funnel.

EXAMPLE 2 Preparation of Improved Functionalized Mesoporous SilicaMCM-41 Type

Briefly, 10 g of OSU-6 powder was refluxed in 100 mL of dry toluene forfour hours in dry atmosphere followed by washing with dry toluene anddrying at 80° C. under vacuum. The resulting material was mixed in 100mL of dry toluene with 20 mL of trimethylamine (TEA) and stirred foraround an hour at room temperature. The obtained solid was filtered offwith a fine filter funnel, washed with 50 mL of dry toluene three times,and vacuum-dried. During the first functionalization step, 3.0 g (˜50mmol) of the TEA-reacted OSU-6 was refluxed with 50 mmol of afunctionalizing agent in 100 mL of dry toluene for 48 hours under N₂atmosphere. The resulting solid mixture was filtered off with a finefilter funnel and washed three times, first with 50 mL of toluene andthen with ethanol to remove any remaining functionalizing agent. Theobtained white solid was dried at 80° C. under vacuum for 24 hours. Thedescribed procedure was then repeated with 2 g of the functionalizedOSU-6 to investigate the effect of the multi-step functionalization onthe density of functional groups attached to the surface of thefunctionalized sorbent.

EXAMPLE 3 Characterization of Properties of Mesoporous Silica

Pore Size and Pore Volume:

This is determined according to the procedure of Barrett-Joyner-Halenda(B J H) model (“The determination of pore volume and area distributionsin porous substances. I. Computations from nitrogen isotherms” inJ.A.C.S. (1951), 73, 373-380). 20-point N₂ adsorption and desorptionBrunauer-Emmett-Teller (BET) isotherms were recorded for each powder.Exemplary nitrogen isotherms for the non-functionalized (FIG. 2A) andmethoxytriethylenoxypropyl-functionalized (MP-functionalized) mesoporoussilica (FIG. 2B) were obtained.

FIG. 2A contains type IV isotherms, which are associated with thecapillary condensation of adsorbate into mesopores, while the observedhysteresis of type A indicates that pores of the mesoporous silica havecylindrical shapes. After functionalization (FIG. 2B), the hysteresisdisappears, and the adsorption-desorption isotherms assumed the shapesof type II isotherms due to the attachment of functional groups to thepore walls.

The pore size distributions of the functionalized and non-functionalizedsorbents analyzed using the BJH model are shown in FIG. 3. The plots ofthe differential volumes versus average pore radii indicate that theaverage pore diameter for non-functionalized mesoporous silica(corresponding to the maximum value of dV/dr) amounts to about 10 nm.However, this value is significantly reduced after functionalization toas low as 2 nm.

The surface area was also determined. The following table summarizes theobserved approximate surface area for some of the different sorbents.

BET Surface Area Measurement Density Decomposition Sorbent (m²/g) (nm⁻²)Temperature/° C. OSU-6 570 N/A OT-OSU-6 390 1.5 215 MP-OSU-6 290 1.2 250BP-OSU-6 420 1.4 145

A decrease in the BET surface area by a factor of about 3-4 or more(from 550 m²/g down to 170 m²/g) was observed for functionalizedmesoporous silica as compared to non-functionalized mesoporous silica.In all cases, the surface coverage of all functional groups (calculatedfrom the results of thermogravimetric analysis and measured BET surfacearea) amounted to 1.1-1.3 groups/nm².

The measured BET surface area was reduced from the initial 570 m²/g forpure OSU-6 to 290-420 m²/g for the functionalized OSU-6 sorbents, whichwas consistent with the presence of various functional groups on thepore surface. In addition, the table also includes the functional groupdensities (per nm² of the OSU-6 pore surface) and the decompositiontemperatures determined from the TGA spectra recorded at a heating rateof 5° C./min. According to the TGA results, the attached functionalgroups with densities of 1.2-1.5 nm⁻² are stable at temperatures below145-250° C. depending on the functionalizing agent. Thus, allfunctionalized sorbates have sufficiently high decompositiontemperatures to allow their use in extreme environments.

Channel Wall Thickness:

This is determined from TEM images using the procedure reported by A.AlOthman and Allen W. Apblett (“Synthesis and characterization of ahexagonal mesoporous silica with enhanced thermal and hydrothermalstabilities”, in Applied Surface Science (2010), 256, 3573-3580). Inbrief, wall thickness is measured using the microscope and by visualcomparison of image details to the image scale.

Confirmation of Functionalization:

Confirmation of functionalization of the mesoporous silica was obtainedby Fourier transform infrared spectroscopy (FTIR).

The FTIR spectrum for the OSU-6 sorbent was characterized by two mainfeatures at 796 and 1052 cm⁻¹ (corresponding to the Si—O—Si silicavibrations) and a small peak at 974 cm⁻¹ resulting from the —OH hydroxylgroups attached to the pore surface. A broad adsorption band wasobserved at around 3400 cm⁻¹ due to the —OH stretching vibrations ofphysisorbed water species. In the octyl- andmethoxytriethylenoxypropyl-functionalized OSU-6, a band representing theC—H stretching vibrations of the attached alkyl groups was clearlyobserved at around 2900 cm⁻¹, while the peaks at 695 cm⁻¹ and 758 cm⁻¹detected for the biphenyl-functionalized OSU-6 were due to the sp² C—Hbending of the attached biphenyl groups.

FIGS. 22A and 22B depict exemplary FTIR spectra for (1) pure OSU-6, (2)methoxytriethylenoxypropyl-functionalized OSU-6, (3)biphenyl-functionalized OSU-6, and (4) octyl-functionalized OSU-6powders.

EXAMPLE 4 Preparation of Sorbent Comprising a Mixture ofNon-Functionalized Mesoporous Silica and Functionalized MesoporousSilica

Method A:

A known amount of non-functionalized mesoporous silica is mixed with aknown amount of functionalized mesoporous silica to provide a mesoporoussilica mixture.

The weight ratio of non-functionalized mesoporous silica tofunctionalized mesoporous silica can range from about 1:100 to about100:1 with all integer and fractional values therein or therebetweenbeing contemplated.

Method B:

Sorbents comprising physical mixtures of one, two or three mesoporoussilicas were prepared according to the following table, which indicatesthe weight percent of each.

OSU-6 MP-OSU-6 BP-OSU-6 Composition (% wt) (% wt) (% wt) 1 100 0 0 2 9010 0 3 80 20 0 4 70 30 0 5 90 0 10 6 80 0 20 7 70 0 30 8 80 10 10 9 7020 10 10 60 30 10 11 70 10 20 12 70 10 30 13 60 20 20 14 50 20 30 15 5030 20 16 40 30 30

The mixtures were prepared by mixing measured amounts of each componentand mixing the components together to form the target composition underambient conditions.

EXAMPLE 5 Preparation of Various Forms of Mesoporous Silica

Sorbent Pellets:

Pure sorbent powder was also pressed into 6-mm and 12-mm circularpellets using a die. The 12-mm pellets were produced by utilizing amanual pellet press (CARVER 4350.L) under an applied force of 2 tons andexposure time of 90 seconds, while the 6-mm pellets were manufactured byan automated pellet press (TDP-7) under 4 tons of applied force (FIG.6). No reduction in surface area at this relatively low pressure wasdetected. Even after pressing the sorbent powder into a pellet, themeasured surface area per gram was not substantially reduced until thepressure reached 8 tons, at which a reduction in surface area of around20-25% was observed. To ensure the durability of the pressed 6-mmpellets, 20 wt. % of cellulose was added to the pure sorbent powderbefore pressing. All pellets were annealed in an oven at 600° C. for 24hours prior to sorption experiments to remove any traces of organicimpurities and the cellulose binder.

Sorbent Thin Film:

A thin film of sorbent was produced using a drop casting techniqueaccording to the method of Zhu et al. (“High-performance humiditysensors based on quartz crystal micro-balance coated with mesoporoussilica MCM-41 thin film” in Materials Technology (2017), 32, 101-104,the entire disclosure of which is hereby incorporated by reference).

Sorbent powder containing 50 wt. % of OSU-6, 30 wt. % of BP-OSU-6, and20 wt. % of BP-OSU-6 was suspended in solvent, e.g. alcohol such asethanol. About 100-200 microgram of sorbent powder was deposited as athin film onto a glass/quartz/polymer surface. Briefly, a suspension ofsorbent powder in ethanol with a concentration of 2 mg/mL was preparedby ultrasonication and then deposited on a substrate surface using apipette. The obtained film was dried in air followed by annealing at 85°C. for 5-10 min inside a furnace to completely remove any trace ofethanol thereby leaving the thin film of sorbent adhered onto thesubstrate.

EXAMPLE 6 Capture/Uptake/Adsorption and Recovery of VOC or SVOC withMesoporous Silica Capture/Uptake

A known amount of mesoporous silica is exposed to a gaseous atmosphere(at ambient temperature (about 22-25° C.) and ambient pressure (about1013 mbar) containing the target VOC or SVOC.

More specifically, the 6 mm diameter sorbent pellets and the target VOCor SVOC were placed in a closed chamber under ambient conditions. Theinterior atmosphere of the chamber was equilibrated under ambientconditions for a period of 15 min or at least 8 hours, whereby volatizedcompound adsorbed onto the sorbent. Uptake of contaminant vapors insidethe sorbent pores was evaluated by measuring the weight gain or uptakeof the target compound material after fixed time intervals. Theadsorption process was considered complete when the sorbent mass stoppedincreasing with time.

The table below indicates the approximate (“about”) uptake capacity andrate of capture for OSU-6 exposed to the listed compounds. The rate ofcapture was obtained by fitting the capture over time data with anexponential function equation corresponding to first-order adsorptionkinetics. FIGS. 4A and 4B depict additional adsorption/desorption data.

Uptake capacity Class Target compound (g/g sorbent) PolynuclearNaphthalene  0.221 ± 0.006* Hydrocarbons (PAHs) Alcohol Ethanol 1.69 ±0.01 Anesthetic (solvent) Diethyl ether 0.762 ± 0.005 DisinfectantChloroxylenol 0.46 Organic acid Acetic acid 2.33 Reactive monomerMethylmethacrylate 2.29 Carbonyl Compounds Acetaldehyde 3.9 ± 0.2Acetone 1.329 ± 0.005 Vinyl acetate 1.34 ± 0.02 Acrolein 1.16 ± 0.05Fuels Hexane 0.94 ± 0.01 Octane  0.98 ± 0.05* Xylene 1.216 ± 0.008Benzene 1.268 ± 0.006 1,2,4- 1.239 ± 0.007 Trimethylbenzene Chlorinatedsolvents Methylene chloride 2.11 ± 0.05 Trichloroethylene 2.10 ± 0.01Organophosphates Dichlorvos  0.286 ± 0.009* Malathion 0.47 NitraminesRDX  0.21 ± 0.03* Pyrethroids Permethrin  0.112 ± 0.007* NitroaromaticsTNT 0.109 ± 0.006 Tetrazoles 1,2,3,4-tetrazole  0.127 ± 0.008*5-aminotetrazole  0.021 ± 0.003* Chlorocarbons PCB 209  0.074 ± 0.005*Organochlorines PCBs/PCDFs/PCDDs *Measured for 6-mm sorbent pellets. Forsamples not marked with an asterisk, the sorbent was in powder form.

Additional evaluations were made to compare side-by-side the uptake ofVOC and SVOC by three different forms of OSU-6. The table belowsummarizes the results observed.

Adsorption Target compound and Saturation its room temperature SorbentCapacity time vapor pressure (OSU-6) (g/g sorbent) (h) AcetaldehydePowder 3.9 ± 0.2 12 (101 kPa) 12-mm pellet 0.33 ± 0.01 2 6-mm pellet1.29 ± 0.03 6 Methylene chloride Powder 2.11 ± 0.05 19 (53 kPa) 12-mmpellet 0.50 ± 0.01 2 6-mm pellet 1.69 ± 0.04 15 Acrolein Powder 1.16 ±0.05 24 (37 kPa) 12-mm pellet 0.37 ± 0.01 5 6-mm pellet 0.77 ± 0.03 8Hexane Powder 0.94 ± 0.01 43 (19 kPa) 12-mm pellet 0.260 ± 0.006 10 6-mmpellet 0.61 ± 0.03 25 Vinyl acetate Powder 1.34 ± 0.02 80 (11 kPa) 12-mmpellet 0.396 ± 0.007 3 6-mm pellet 1.08 ± 0.04 10 Benzene Powder 1.268 ±0.006 70 (10 kPa) 12-mm pellet 0.327 ± 0.003 10 6-mm pellet 1.06 ± 0.0530 Xylene Powder¹ 1.216 ± 0.008 750 (1.1 kPa) 12-mm pellet 0.334 ± 0.00915 6-mm pellet 0.85 ± 0.08 10 1,2,4-trimethylbenzene Powder 1.239 ±0.007 2000 (0.28 kPa) 12-mm pellet 0.394 ± 0.007 100 6-mm pellet 1.2 ±0.1 100 Naphthalene Powder (0.013 kPa) 12-mm pellet 0.274 ± 0.005 40006-mm pellet 0.221 ± 0.006 900

The capacity typically increased for the three different forms ofsorbent in the following order: 12-mm pellet<6 mm pellet<powder, meaningthe powdered sorbent typically exhibited the highest capacity. Thesaturation time typically increased for the three different forms ofsorbent in the following order: 12-mm pellet<6 mm pellet<powder, meaningthe powdered sorbent typically exhibited the highest saturation time.

Recovery by Solvent Extraction

In some embodiments, recovery was conducted by solvent extraction. Thecompound-loaded sorbent was treated with solvent known to be able todissolve the target VOC or SVOC. A sample of the compound-containingsolvent was then analyzed by GC/MS (gas chromatograph equipped with massspectrometer detector). In order to develop calibration curves, controlsamples of sorbent (25 mg) containing known amounts of target compoundwere prepared by placing known amounts of sorbent on a microbalance andspiking the sorbent with known amounts of target compound. Sorbent wasthen extracted with a predetermined amount of solvent (2.0 g) andaliquots of the compound-containing solvent were analyzed by GC/MS.

Extraction was performed with 2 mL of acetonitrile, and analyses wererun with the GC/MS in the SIM mode using the known molecular weights ofthe target compounds. The detection limits and quantitation limits werecalculated from the average number of counts and the standard deviationof nine blank samples. Using these protocols, the amounts of theanalytes sorbed in OSU-6 when exposed at their PEL limits for 15 minutesand 8 hours were determined.

Quanti- Recovery Detection tation efficiency limit limit Class Targetcompound (%) (ng) (ng) Polynuclear Naphthalene 92.9 5920 7220hydrocarbons Carbonyl Acetaldehyde compounds Acrolein Vinyl acetate 100162 212 Fuels Benzene 97.0 16.4 20.9 n-Hexane 100 55.8 92.8 n-Octane96.2 55.9 71.1 1,2,4- 92.3 10.3 18.0 Trimethylbenzene o-Xylene 94.9 19.626.2 Chlorinated Methylene 99.7 145.1 375.2 solvents chlorideTrichloroethylene 91.1 22.1 29.4 Organophosphates Dichlorvos 96.6Nitramines RDX 3830 4130 Pyrethroids Permethrin Nitroaromatics TNT 82.518.9 30.8 Tetrazoles 1,2,3,4-tetrazole 84.5 1240 2050 5-aminotetrazoleChlorocarbons PCB 209 organochlorines

EXAMPLE 7 Determination of Thermal Stability of Adsorbed Compound(s)

The stability and desorption kinetics of the captured compounds from thesurface of non-functionalized and functionalized sorbent powders wasdetermined by thermal desorption and thermogravimetric analysis (TGA).

Glass vials containing compound-loaded sorbent powders, 12-mm pellets or6-mm pellets were provided. The sorbate content in the sorbent pores,i.e. the weight of the sorbent powder, was monitored as a function oftemperature in the range from about 25-200° C. (which was ramped at arate of 5° C./min in a thermogravimetric analyzer). The table belowlists the maximum desorption temperatures obtained from the TGAexperiments for some of the tested compounds adsorbed on the surfaces ofnon-functionalized and functionalized OSU-6 sorbent powders with initialcontents of VOC or SVOC between 15 and 40 wt. %.

OSU-6 OT-OSU-6 BP-OSU-6 MP-OSU-6 (° C.) (° C.) (° C.) (° C.) Hexane 5044 45 43 Benzene 63 41 45 46 Xylene 110 86 80 95 Acetaldehyde 52 43 4245 Vinyl acetate 53 45 51 54 1,2,4-trimethylbenzene 130 100 105 110Acrolein 50 48 46 52 Naphthalene 140 110 145 120

An exemplary thermograph for desorption of benzene from the abovedifferent sorbents is depicted in FIG. 5.

EXAMPLE 8 Determination of Storage Stability

The storage stability of the compound-loaded sorbent toward desorptionupon long-term storage was determined.

VOC-loaded or SVOC-loaded sorbent was placed inside an evaluated andchosen zip-locked Poly Mylar bag with a tear notch and its stabilitymonitored at different temperatures. In addition, short-term storagestudies were completed for a subset of the compounds (acetaldehyde,acrolein, benzene, and vinyl acetate) in zip-locked Poly Mylar bags at+24° C., which were subsequently analyzed by both mass spectrometry andby measuring the mass change after 1, 3, 6, 9, and 14 days. This datadeveloped a case for using PVDF (polyvinylidene fluoride) bag having awall thickness of at least 3 mil as a viable and practical container forthe sorbent/dosimeter transfer to and from the field. Those bags exhibithigh stability, high melting point, low sorption capacity and chemicalinertness. As a control and to quantify the moisture effect on thestored bags, unexposed OSU-6, activated carbon, and Tenax samples wereprepared for each storage batch.

The mass changes measured with respect to the sum of the sorbent andsorbate masses were determined. Negative values denoted mass losses,while positive values denote the mass gain potentially due to moistureadsorption. As a control and to quantify the moisture effect on thestored bags, blank OSU-6, activated carbon, and Tenax samples (without acontaminant) were prepared for each storage batch.

Two “industry-standard” sorbent media (activate charcoal and Tenax TA6-80) served as control groups for long-term storage studies. Selectionof the specific grade of activated charcoal was based on the informationpresented in the OSHA Technical Manual (Section II: Chapter 1, PersonalSampling for Air Contaminants). The standards listed in that documentwere derived from the OSHA research efforts conducted at the Salt LakeCity Technical Center (SLTC) and the Cincinnati Technical Center (CTC),which were subsequently validated by both OSHA and NIOSH for airmonitoring applications. “Charcoal Tubes” containing 100 mg of 20 meshactivated charcoal and 50 mg of 40 mesh activated charcoal were used thesorbent media utilized for OSHA-approved monitoring techniques. Tenax TA60-80 mesh was selected as the polymer-based sorbent media standard.

Storage samples for the sorbent of the invention analyzed after 60 daysof storage at room temperature did not exhibit any decomposition orcontamination products.

Data available indicated very long storage stability (over 3 years) formethylene chloride adsorbed onto the mesoporous silica of the inventionwhen the methylene chloride-loaded sorbent samples were stored in afreezer. The samples retained the original mass spectrometry methylenechloride (m/z=49) intensity and showed no contamination or decompositionproducts. The obtained data provides preliminary feasibility towards thepossibility of establishing an Exposure Monitor Repository where thedosimeter sorbent media can be stored for substantially longer periods(months to years) and retroactively analyzed as new methodology or newprioritized target compounds emerge.

Storage stability in terms of desorption of the VOC or SVOC from thesorbent was evaluated under the same conditions set forth above. OSU-6with no compound adsorbed thereon was used as a control in order toaccount for the change in weight due to moisture sorption/desorptionduring the study period. The weight of the sorbent was measured on aweekly basis. The data (FIG. 7) indicate little to no compound (sorbate)was lost from the sorbent upon extended storage at room temperature(about 24° C.) and ambient pressure over a period of 14 weeks, when thedata was normalized for variation due to moisture sorption/desorption.

EXAMPLE 9 Comparison of Non-functionalized and Functionalized MesoporousSilica

The procedure of Example 6 was followed with the exception that eithernon-functionalized mesoporous silica or functionalized mesoporous silicawas used. The following table summarizes the uptake capacities (g/gsorbent) for selected target analytes on OSU-6 and functionalized OSU-6sorbents.

OSU-6 OT-OSU-6 BP-OSU-6 MP-OSU-6 Methylene 2.28 ± 0.08 1.86 ± 0.04 1.83± 0.05 1.69 ± 0.05 chloride Hexane 1.14 ± 0.01 0.91 ± 0.02 0.90 ± 0.030.83 ± 0.02 Benzene 1.49 ± 0.03 1.20 ± 0.02 1.17 ± 0.02 1.09 ± 0.02Acetaldehyde 2.2 ± 0.1 1.14 ± 0.02 1.21 ± 0.05 1.38 ± 0.09 Vinyl acetate1.58 ± 0.04 1.24 ± 0.02 1.24 ± 0.02 1.15 ± 0.03 Trichloro- 2.53 ± 0.032.03 ± 0.05 1.98 ± 0.03 1.79 ± 0.04 ethylene Acrolein 1.45 ± 0.05 1.44 ±0.08 1.29 ± 0.08 1.29 ± 0.08

The data indicate that the uptake capacity of the sorbent decreases withsurface functionalization which is mainly due to reduced surface area;however, an advantageous increase in the rate of uptake for specifictarget compounds was observed for the functionalized mesoporous silica.

EXAMPLE 10 Determination of Sampling Rate for VOC and SVOC

Sampling rates were determined for a wide range of compounds includingn-octane, trichloroethylene, n-hexane, naphthalene, and TNT adsorbed onthe surface of non-functionalized OSU-6 at exact PEL exposures for 15min and 8 h inside a dosing chamber. The mass gain obtained after thesorbent exposure to analyte vapor is related to the sampling rate viathe following equation, where M is the mass gain in ng, SR is thesampling rate in cm³/min, C is the concentration of analyte vapor inmg/m³, and t is the exposure time in min.M=SR×C×t

The sampling rate SR can then be expressed as follows:

${SR} = \frac{M}{C \times t}$

The values of M were obtained from the results of the recovery via thesolvent extraction technique described above. The calculated samplingrates are listed in the table below.

OSHA Sampling rate PEL (mL/min) Target limit XploSafe XploSafe Classcompound (ppm) (15 min) (8 h) Polynuclear Naphthalene 10 — 3.3hydrocarbons Carbonyl Acetaldehyde 100 32.1 3.2 compounds Acrolein 0.1Vinyl acetate 10 3.6 3.9 Fuels Benzene 1 6.6 5.2 n-Hexane 50 12.7 2.8n-Octane 300 6.8 2.7 1,2,4- 25 4.1 2.9 Trimethylbenzene o-Xylene 100 2.01.7 Chlorinated Methylene 25 108.9 15.4 solvents chlorideTrichloroethylene 100 1.7 0.88 Organophosphates Dichlorvos 0.1 12.5 11.5Nitramines RDX 0.2 Pyrethroids Permethrin 0.3 Nitroaromatics TNT 0.2 —0.25 Tetrazoles 1,2,3,4-tetrazole — 5-aminotetrazole — Chlorocarbons PCB209 0.025 organochlorines

EXAMPLE 11 Evaluation of Dosimeters

The clip-on dosimeter badge prototypes were exposed to vanillin vapors.The vapors originated from four open containers of 3″ in diameter thatcontained 2 g of pure vanillin powder placed inside an office room withdimensions of 15′×17′×7.5′. Two different experiments were conducted for15 min and 8 h, corresponding to the standard short-term and long-termOSHA exposures. It must be noted that the maximum vanillin concentrationin air corresponding to that of its saturated vapor is very low and isequal to 0.16 ppm.

The sorbent from the dosimeter badge exposed to vanillin was analyzed bya mass spectrometer (MS), and the obtained results are listed in thetable below.

Vanillin MS Exposure intensity Estimated vanillin Sample time (m/z =151) content Vanillin powder — 800,000 0.1 mg Dosimeter sorbent 15 min<500 Less than 0.06 microg Dosimeter sorbent 8 hours 4,000 Less than 0.5microg

The dosimeter exposed to the air containing vanillin vapor for 8 hoursexhibited two characteristic mass spectrometry peaks at m/z=151 and 152with the peak ratio identical to that of pure vanillin vapor. While thedosimeter exposed for 15 minutes recorded significantly lower amounts ofvanillin vapor (see Table 10), it is consistent with the very lowpressure of vanillin vapor at room temperature (1.6×10⁻² Pa). Due to thevery high sensitivity of the MS analyzer to vanillin vapor, theintensity of 800,000 corresponds to the vanillin powder amount as low as0.1 mg. Thus, the upper limit of the adsorbed vanillin amount can beestimated from the intensity ratios listed in Table 10. For sorbentsample exposed to vanillin vapor for 8 hours, the adsorbed vanillincontent would be below 0.5 micrograms, which also corresponds to theestimated sampling rate of around 1 mL/min.

The above is a detailed description of particular embodiments of theinvention. It will be appreciated that, although specific embodiments ofthe invention have been described herein for purposes of illustration,various modifications may be made without departing from the spirit andscope of the invention. Accordingly, the invention is not limited exceptas by the appended claims. All embodiments disclosed and claimed hereincan be made and executed without undue experimentation in light of thepresent disclosure.

All integers and fractions within the limits/ranges specified herein arecontemplated.

The invention claimed is:
 1. A device for passive sampling of volatileorganic compound or semi-volatile organic compound in air or gaseousenvironment, the device comprising: a sorbent holder comprising one ormore unsealable or resealable chambers, at least one of said chamberscomprising one or more portions of mesoporous silica sorbent of theMCM-41 type (hexagonal), wherein the mesoporous silica possesses acombination of two or more of the following physical properties:Property Linear formula SiO₂ polymer Pore structure Hexagonal tubes Poresize (diameter) about 2 to about 30 nm Pore volume about 0.5 to about2.0 cm³/g Surface area greater than about 600 m²/g Channel wallthickness about 1 to about 5 nm;

and wherein said sorbent excludes porous polymer.
 2. The device of claim1, wherein the mesoporous silica comprises: a) at least onenon-functionalized mesoporous silica; b) at least one functionalizedmesoporous silica; or c) a combination of one or more non-functionalizedmesoporous silica and one or more functionalized mesoporous silica. 3.The device of claim 2, wherein the weight ratio of non-functionalizedmesoporous silica to functionalized mesoporous silica range from about1:100 to about 100:1.
 4. The device of claim 1, wherein the sorbent hasbeen functionalized with one or more adsorption modifier functionalgroups that improve in at least one aspect the adsorption of particularVOC or SVOC.
 5. The device of claim 4, wherein: a) the one or moreadsorption modifier functional groups are covalently bound to the porousmedium; b) the one or more adsorption modifier functional groups arenon-covalently bound to the porous medium; c) the mass content offunctional groups in the porous medium as determined bythermogravimetric analysis is in the range of 20-25%; or d) acombination of any two or more thereof.
 6. The device of claim 1,wherein the sorbent is silane-functionalized mesoporous silica.
 7. Thedevice according to claim 6, wherein the silane functionalizedmesoporous silica has been functionalized by treating unfunctionalizedmesoporous silica with a trialkoxyalkylsilane (R¹Si(OR²)₃), wherein: R¹is selected from the group consisting of aromatic group, alkyl group,oxygen-containing alkyl groups, sulfur-containing alkyl groups,nitrogen-containing alkyl groups, phenyl, biphenyl, (C1-C8)-alkyl,methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl,decanyl, undecanyl, methoxytriethyleneoxypropyl, alkoxyalkyleneoxyalkyl,haloalkyl, halo-(C1-C8)-alkyl, aminoalkyl, alkoxyalkyl, polyaromatic,toluyl, fluoroalkyls, fluroaromatics, and their combinations; and R² isselected from the group consisting of alkyl, C1-C12-alkyl, with methyl,ethyl, and propyl being preferred, thereby forming asilane-functionalized mesoporous silica comprising plural silane groupsR¹Si— covalently bound to oxygen molecules of the mesoporous silica. 8.The device of claim 6, wherein the silane functionalized mesoporoussilica comprises functional groups with a chemical formula defined as—Si(R¹)(OR²)_(n)—O_(m)—, wherein: R¹ is selected from the groupconsisting of aromatic group, alkyl group, oxygen-containing alkylgroup, phenyl, biphenyl, C1-C8-alkyl, methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, nonyl, decanyl, undecanyl,methoxytriethyleneoxypropyl, alkoxyalkyleneoxyalkyl, haloalkyl,alkoxyalkyl, polyaromatic, and toluyl; R² is selected from the groupconsisting of alkyl, C1-C12-alkyl, methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, nonyl, decanyl, and undecanyl, thereby forming asilane-functionalized mesoporous silica comprising plural silane groupsR¹Si—covalently bound to oxygen molecules of the mesoporous silica; andwherein n is 0, 1 or 2, and m is 2, 1, or 0, respectively.
 9. The deviceof claim 1, the sorbent releases at least 75 wt % of adsorbed VOC orSVOC when the sorbent is exposed to heat or organic solvent.
 10. Thedevice of claim 1, wherein the sorbent releases less than 25% of VOC orSVOC during storage at ambient temperature for a period of at least 1week.
 11. The device of claim 1, wherein said sorbent holder comprisestwo or more separate and independently unsealable and independentlyresealable chambers, wherein a first one of said chambers comprises afirst portion of said sorbent, and a second one of said chamberscomprises a second portion of said sorbent.
 12. The device of claim 11further comprising a diffuser comprising plural ports, pores orperforations.